Insulating cap for the joints of electrical conductors and conductive coating for use therein



J1me 1930. F. M. -VAN GELDEREN 6 ,039

INSULATING GAP FOR THE JOINTS OF ELECTRICAL CONDUCTORS AND CONDUCTIVE COATING FOR USE THEREIN Filed Oct. 3, 1927 Patented June 3, 1930.

PATENT OFFICE EBEDERIK MARIN'U'S VAN GELDEREN, OF ENSGHEDE, NETHERLANDS INSULATING CAI FOR THE .romirs or anncrmcar. connoorons AND connuc'rrvn coa'rme FOR use 'rnnnnm Application filed October 8, 1927. Serial No. 223,789.

This invention relates to insulating caps for the joints of electrical conductors and more particularly to caps for receiving, binding and insulating the bare ends of electrical conductors, of the general type shown n my prior Patents Nos. 1,460,624 and 1,513,656 and of which the present invention is a further improvement.

A primary object of the invention is to provide a one-piece device in the use of which any doubt as to reliable electrical connection between the ends of the conductors to be insulated is entirely removed.

Another object of the invention is to provide an insulating cap which can be as readily applied to the conductors as any of the known devices of the type and which will be easier to apply than certain forms hitherto known, and one which may be very inexpensively manufactured.

Another object of the invention is to produce a novel conducting medium, suitable especially for application to the inside of such insulating ca s and also suitable for application to sur aces in general whereon it is desirable to produce an electrically conductive area or zone.

Broadly the invention comprises an insu lating cap having a cavity therein for the reception of the ends of the conductors and provided with an internal thread for binding engagement with the bare ends of the conductors when the cap is applied thereto and rotated, and a conductive coating on the thread. v

Furthermore, the invention comprises as a conductive coating what I have chosen to call a metal glaze, the same being composed preferably of a glaze of known variety having incorporated therewith the requisite pro portion of a metal in finely divided form.

The invention will be readily understood by reference to the accompanying drawing, wherein:

Fig. 1 is a longitudinal section of one'form of insulating cap having the electrically condpctive coating applied to the interior there- 0 Fig. 2 is a similar view of a cap, the cavity whereof is of somewhat different form;

' Fig. 3 is a similar view of still another form of cap, and I Fig. 4 is a similar view of a form in which the thread is confined to the inner bore.

In said drawing, the numeral 1 represents an insulating cap of porcelain or other suitable insulating material. The cap is hollow as shown and the wall of the cavi is provided with a thread 2. The threa may be continuous or uniform throughout the cavity as shown in Fig. 1; or, as shown in Fig. 2, the cavity may consist of two conical or tapering bores, the larger one near the opening of the cap and an inner bore of smaller 'dlameter than the first opening into the latter. To facilitate introduction of the conductors into the inner bore, especially for use with conductors composed of a plurality of strands of wire, the inner end of the outerbore may coincidewith the outer end of the inner bore as shown, but such an arrangement is not necessary, and a shoulder may be formed at the bottom of the outer threaded portion. Preferably the thread 3 within the smaller bore is slightly rounded as shown in Figs. 2 and 3, while as indicated by the numeral 4 the thread in the outer bore of the cap of this form is relatively sharp. The thread need not be continued along the outer bore which engages the insulation on the conductors, and a form in which this portion 8 of the cavity is left smooth is shown in Fig. 4. As illustrated in Fig. 3, the inner portion 5 of the cavity may be only slightly tapered. In any case the thread is'adapted to receive and provide a binding engagement with the bare ends of the conductors when the cap is ap lied thereto and rotated,'and if, as referre the material of the shell of the cap 1s harder than the metal of the conductors, the thread-on the inner portion of the wall of the cavity cuts or tends to cut a spiral way or thread into the surface of the united conductors.

In accordance with the present invention, a thin conductive coatin is applied to the thread in the cavity of t e-cap as indicated at 6 in the several views. Since the coating is intended to contact only with the bare ends of the conductors and not with the insulation 7 thereon which may be engaged by the outer moved, e. g. by suction.

portion of the thread, such coating is preferably confined to the inner portion of the .a fraction of a millimeter 1n thickness, usually not more than 1/64th of an inch, is preferably composed of a metal glaze. The latter may be prepared as follows:

From 50 to parts by weight of powdered metal, preferably copper, alt ough any other suitable metal such as nickel or silver may be emplo ed, is mixed at ordinary temperature with rom 50 to 25 parts of a glaze of any known and suitable variety, such as a borate glaze, commonl lead borate. The mixture is milled in a bal or pebble mill until a true suspension is obtained, and, if desired, a little colloid such as glue may be added to accelerate the action desired.

The metal glaze may be applied to bodies -or surfaces which it is intended to render electrically conductive in almost any of the ways known for applying liquid-coatmg compositions in general, but for-the application thereof to insulating caps of the type described and by the method hereinafter referred to the product should be relatively thin, its consistency being about that of milk.

The metal glaze is (preferably, althou h not necessarily, applie by introducing t e liquid into the bottom of the cavity by means of a syringe until a pool of the desired height along the wall of the cavity is formed, whereupon tho excess liquid is immediately re- The coatin which remains on the inner wall of the cap 1s dried and is then baked in b mufiling in an ordinary enameling oven, or example, for three or four minutes. In case the metal employed is copper, the baking must of course take place 1n a non-oxidizing atmosphere. The coating thus formed becomes substantiall integral with the porcelain of the shell of the cap.

According to the mode of ap lyin the coating described above, both t e t read proper and the groove will receive the film of metal glaze. The thread alone may be coated with the conductive medium, although it is about as economical and more practical to coat both the thread itself and the groove. It is to be understood however, that in the use of the expression on the thread or on said thread in the appended claims I intend to include a conductive coatin within the cavity whether it covers only t e thread in the strict sense or both the thread and groove.

When an insulating cap, as described herein, is applied to the bare ends of electrical conductors, a continuous and dependable electrical connection between the conductors.

is effected, without impairing the stren h of the mechanical connection, and the evice therefore provides in a single piece what has .vided with an internal thread for bin ing engagement with said bare ends when the cap is applied thereto and rotated, and a conductive coating ofmetal glaze on said thread.

2. An insulating cap for the bare ends of electrical conductors com osed of a non-conductive material which is harder than the metal of the conductors, said cap having a tapered inner cavity therein for the reception of said bare ends, the wall of said cavity' having an integral thread for binding engagement with said bare ends when the cap is applied to the conductors and rotated, said thread being slightly rounded, and a tapered outer cavity the inner end whereof mer s into said inner cavity and the wall of WhlCh is provided with a relatively sharp thread for bindin engagement with the insulation on the conductors, and a conductive coating of metal glaze on the thread in said inner cavity.

3. An insulating cap for the bare ends of electrical conductors havin a cavity therein, the wall whereof is provi ed with a thread integral with the material of the cap, and a conductive coating of metal glaze within the cap confined to the thread in the inner portion of said cavity. v

4. An insulating cap for the bare ends of electrical conductors comprising a porcelain cap having a ta ered cavity therein provided with an interna screw thread, and a conductive coating of metallic glaze on the threaded wall of the inner portion of said cavity.

In testimon whereof, I afiix my si ature.

FREDEliIK M. VAN GELDE EN. 

